Dynamic monitoring and control of jigs

ABSTRACT

The monitoring and control of jig separators is effected by monitoring the time variation within a jig cycle of at least one operating parameter of the jig, and manipulating the operating parameter(s) to produce the sought after form of the time variation within the jig cycle. Operating parameters include bed voidage, water level, particle velocity in the bed and water or air pressure.

BACKGROUND OF THE INVENTION

(1) Field of Invention

THIS INVENTION relates to the dynamic monitoring and control of jigs.

(2) Prior Art

The University of Queensland has patented and developed a control systemfor jigs that is centred on the concept that the jig can be controlledin response to measurement of the time variation of a signal during acycle for the jig pulsation. The idea of signal averaging over a numberof jig cycles is also invoked to provide more accurate signals and thePatent refers particularly to the measurement of density in the jig bedas a function of time. The Abstract of Australian Patent No. 596858(AU-B-76489187) states:

"The density of the material in the jig bed is measured in consecutiveshort segments over the jig cycle, the time period of each segment notbeing greater than one-tenth the cycle time of the jig, to determine thedensity signature or profile of the jig. By controlling the operatingparameters (e.g. inlet and outlet valve opening and closing, underbedwater flow rate, discharge gate position and jig working air (pressure)of the jig, the density signature or profile is maintained within acontrol envelope for efficient stratification of the mineral."

It is relevant to outline some basic aspects of the physics of operationof jigs, including centrifugally-aided jigs also known as Kelsey jigs.These concepts are also applicable within minor modification to movingscreen jigs.

The separation in a jig occurs as a result of the passage of a pulsatingflow of water through a bed of particles that are supported on a screenor punched plate. As the water flows through the screen and into the bedof particles (pulsion phase of flow--consider such a flow direction tobe positive or `upward`), the fluid drag on the particles supports moreand more of the weight of the bed of particles until at some criticalvelocity, the bed of particles lifts. Further increase in fluid velocitycauses fluidisation and dilation (decrease in the volume fraction ofsolids) of the bed. As the pulsion phase of the flow finishes and thefluid velocity reverses and increases in velocity downwards, thedilation of the bed rapidly decreases and the bed is forced back againstthe bed plate. Further increase in the downward velocity causes asignificant pressure drop to develop across the bed.

Superimposed on this pulsating flow is a relatively small constantupflow of water through the bed. The purpose of this flow is to supply acurrent of water above the bed plate that will assist in the transportof the particles in a direction perpendicular to the pulsing flow. In acontinuous jig, the particles of coal or mineral are transported fromthe feed end of the jig to the discharge end and the bed becomesprogressively more stratified or better separated or better sorted asthe material moves from the feed end to the discharge end.

The extent of separation is gauged by the extent to which particles ofdifferent size and true particle density become sorted in the bed. Forexample, for a particle bed composed of only one size of particle, buthaving a range of particle densities, an arrangement of particles in thebed such that particle density decreases monotonically from the bedplate towards the top of the bed would be considered to be perfectlysorted or separated.

The manner in which particles of differing density move from one layerto another in the bed as separation progresses depends on the extent towhich the particle bed dilates and the relative vertical motion of theparticles in response to the fluid flow through the particle bed. When abroad distribution of particle sizes exists in the bed, particle motioncan also occur in the bed by a trickling mechanism wherein smallparticles move through the interstices of the packed bed.

One must also distinguish between two general methods of jiggingseparation, namely `through the screen` separation or `over the screenseparation`. In the first case, the bed becomes stratified or sortedwith high density particles moving towards the bed plate and low densityparticles moving towards the top of the bed. If the apertures in the bedplate are sufficiently large, particles of high density material maypass through the plate into the space (known generally as the hutch) onthe other side of the bed plate for collection. Generally, when highdensity particles are concentrated in this way, a quantity of relativelylarge relatively high density particles are added to the bed with theintention that these particles shall remain in the bed next to the bedplate and form a `ragging` bed through the interstices of which thesmaller particles to be concentrated may move. In the second case ofover the screen separation, no ragging is added and the entire mass offeed material is allowed to stratify under the influence of thepulsations. A means of splitting the bottom layers of the bed from theupper layers of the bed is provided at the discharge end of the jig sothat high density and low density products are recovered from theseparator.

Finally, one must note that through the screen and over the screenjigging mechanisms of separation can function simultaneously in a jig.

SUMMARY OF THE INVENTION

Since application for Australian Patent No. 596858, the concepts ofcontrol for jigs have developed in accordance with the invention toinclude control of the water motion of the jig in response tomeasurements of the dynamic water level and other signals in the jig,amongst other concepts. More generally, control of jigs so as tomaintain constant in form the time variation of measured signals, otherthan bed density, that can be considered to be linked to the performanceof the jig has been developed.

Not only can the form of the time variation of a signal from the jigprovide a source signal for automatic control actions, but also thesignal itself can be considered as a `signature` whose particular formindicates correct operation of the jig and departure from that formindicates abnormal operation or indicates a change in the nature of thematerial or be separated. The recognition of the form of the signal as asource for control action includes the concept of the form of the signalas a `on-line diagnostic tool` for jigs.

The most important fact relating to the operation and control of a jig,in terms of the separation or sorting achieved in the bed is that theseparation or sorting is principally influenced by the nature of thefluid flow through the bed as a function of time within the jig cycle.Given that the design of the jigging separator permits the feeding anddischarge of materials in an orderly manner, the settings andadjustments on the jigging machine are relevant to control only in sofar as they combine to produce a particular variation of the water flowwith time within the jig cycle. It may happen that the combinations ofsettings on the jig controls are such that they do not uniquelydetermine the water motion in the jig. That is to say, that more thanone different combination of settings will produce effectively the samewater motion in the jig and hence the same rate and degree ofseparation.

Because of the relationship between the fluid flow (velocity andacceleration) through a bed of particles and the pressure drop acrossthe bed of particles it is generally true that measurement of fluidpressures at points within or across the particle bed can be used to agreater or lesser extent to infer the state of motion of the waterthrough the particle bed.

It is possible to design instrumentation for immersion in the bed of ajig that permits the determination of the porosity or voidage (volumefraction fluid) in the bed and the variation of voidage as a function oftime within the jig cycle. Such instrumentation also permits deductionof the state of fluid motion through the bed as the voidage as afunction of time within the jig cycle is, for a given average bedcomposition, uniquely determined by the water motion.

It is possible to design instrumentation for immersion in the bed of ajig that permits the determination of the velocity of particles as afunction of time within the jig cycle.

It is an object of this invention to provide a means of control of a jig(conventional or centrifugal jig or separation in any pulsatingseparator operating in a manner substantially similar to a jigseparator) according to a procedure that relies on the determination ofvarious sensor signals from the jig (their time variation within a cycleof the jig) to control the operating parameters of the jig.

It is a further object to provide a jig (as hereinbefore described)provided with such controls.

It is a further preferred object to provide a control system which doesnot employ nucleonics.

Other preferred objects will become apparent from the followingdescription.

In one aspect, the present invention resides, for conventional (workingunder gravity) jigs, centrifugal jigs, and moving screen jigs (workingunder gravity or centrifugal force, the method of monitoring the jigs bymeasurement (and optional display) of the time variation within a jigcycle of at least one signal such as bed density, bed voidage, waterlevel, velocity or acceleration in the jigging or air chamber, particlevelocity or acceleration in the bed or water or air pressure.

In a second aspect, the present invention resides, for such jigs, in theautomatic control of jigs based on the use of the form of the timevariation within a jig cycle of such signal(s) wherein one or more ofthe operating parameters of the jig are manipulated in order to producethe sought-after form of the time variation of the signal within a jigcycle.

In a third aspect, the present invention resides in such jigs monitoredand/or controlled by the method hereinbefore described.

With the exception of the aforementioned Australian Patent No. 596858,the prior art in the monitoring and control of jigs has never consideredthe full variation of any kind of signal within the jig cycle. Forexample, it is known to have a standpipe communicating with the regionbeneath the bed plate of a jig at one end and open to the atmosphere atthe other end and a means of measuring the water level in thatstandpipe. It is also known to have a standpipe the same as thatmentioned but closed to the atmosphere with a gas space in the top ofthe pipe and a pressure gauge in the gas space. The peak pressure in thepipe or peak water level in the tube is taken as an indication of thecondition of the jig bed and control actions are taken in response tothe pressure or level. It is also known to measure the water level inthe air chamber of a Batac jig and to apply a control action to the airvalves of the jig in order to prevent the maximum or minimum level ofthe water from reaching certain values.

It is also known to use a `float` (hollow metal tank of particularweight and volume with stem attached) to attempt to sense a positionwithin the coal bed that has a certain mean density in its undilatedstate, and to control the discharge of high density material from thejig bed in response to the float position.

It is also known to employ water level sensors above the jigging chamberof a jig so as to sense the maximum and minimum positions of the waterin the jigging chamber and to use these discrete signals in conjunctionwith the sensing of a critical position of the jig bed float to sequencethe inlet and exhaust valves.

It is also known to employ a density gauge operating on nucleonicprinciples, set at a particular horizon or plurality of horizons tosense some coal bed density value in the jig and to regulate thedischarge in response to this measurement. The coal bed density sensedmay be a time average value over the jig cycle or the density of the bedin the collapsed state or the actual time variation of the densityduring a cycle.

There are a wide variety of control actions that may be taken inresponse to various signals from the jig as there are a number ofoperating conditions of the jig that can be manipulated. Some of theseare:

(i) control of inlet or outlet air valve port area in air driven jigs;

(ii) control of opening and closing times of air valves in air drivenjigs;

(iii) control of operating air supply pressure in air driven jigs;

(iv) control of the mass flow of gas into the air chamber by acombination of means (i) and (ii)

(v) control of oscillation frequency (jig pulsation frequency) in anykind of jig;

(vi) control the diaphragm motion in diaphragm or centrifugal jigs;

(vii) control of the motion of the bed plate in moving plate jigs;

(viii) control of the centrifugal force in centrifugal jigs;

(ix) control the mean level of water in the air chamber of an air drivenjig.

The manner of determination of the control actions to be applied to theabove variables may be via specialised controllers functioning in ananalog or digital fashion and may include computational analyses ofsignals and jig responses via Fourier decomposition methods. The mannerof determining the control action may also include the real-timecomputation of the expected jig response to a control action using amathematical model of the jig. The control action to be taken mayadditionally include the real-time estimation of the physical parametersof the jigging system (for example (but not limited to), bed mass or bedpressure drop) followed by calculation of jig operating settings, bothusing a mathematical model of the jig. This latter method of control canbe considered to be feed-forward control of the jig combined withreal-time identification of jig parameters; it could also be describedas self-tuning control of the jigs.

BRIEF DESCRIPTION OF THE DRAWINGS

To enable the invention to be fully understood, a preferred embodimentwill now be described with reference to the accompanying drawings, inwhich:

FIG. 1 is an elevation (side view) of a schematised jig with associatedmeasurement sensors and controls;

FIG. 2 is a further side view of the jig showing the discharge mechanismand general flow of material through the jig. (We note, however, thatthe discharge mechanism of the jig is not a required feature of the jigin some types of jigs); and

FIG. 3 shows the cyclical (one cycle) of variation of the pressure underthe bed of the jig.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a schematicised drawing of a Baum-type jig with a jig bed17 composed of a high density layer 17B and a lower density layer 17Asupported on a screen plate 24. FIG. 2 shows a side view of th jiglooking from the side remote from the air chamber 16. FIG. 2 shows a bedgauging device 20 immersed in the bed 17 and a stylised device 23 forregulation of the rate of flow of higher density material out of thebottom of the bed before the lower density layer passes into the nextchamber (shown in dotted lines) and marked as 29. Both the device 20 andthe device 23 communicate with the jig controller 2. This controller hasmarked a set input 1, signal inputs 3 (some not shown in both FIGS. 1and 2) and outputs 4 (some not shown in both FIGS. 1 and 2). Alsocommunicating with the jig is the flow of unseparated feed material orstream 26 (which may be combined with water), hutch water addition 19via control valve 21 and supply of compressed air 5 to the air chest 9via a flow controlling device 6. Low density product is withdrawn at 28and high density product is withdrawn at 27. The pulsing flow of waterthrough the screen plate 24 is indicated as 25. The tact that thesediagrams illustrate a conventional Baum-type jig is not meant to limitthe applicability of the means of control to such types of jigs in anyway. The admission and exhaust of air from the air chest to the airchamber 16 is via inlet valve 11 and outlet valve 10 (these valves maybe combined in a single assembly without loss of generality); stream 15indicates exhaust air passing to the atmosphere or other device. Airinlet and exhaust valves are not illustrated for the second chamber 29.

In addition to the bed gauging device 20, the jig is equipped with anunder-bed pressure sensor 18, gas pressure sensors 22 and 7, and levelsensors 13 and 14 in the air chamber and jigging chamber respectively.Such a degree of instrumentation is generally sufficient for theimplementation of the control systems.

The general problem of control of a jig involves two principalcomponents, namely, control of the pulsation in the jig and control ofthe discharge of the products of the separation. (Herein, control of thepulsations is of primary concern).

It was stated above that the stratification in a jig bed is primarily aresult of the nature of the flow of the pulsing water through the jigbed. A comprehensive overall control system for a jig can be constructedin the following way, based on the existence of a mathematical model ofthe motion of the water in the jig. In general, such a mathematicalmodel will include a description of the flow through the supply valve 6,the inlet and exhaust valves 11 and 10 and the hutch water supply valve21, coupled with dynamic material balances on the air in the air chest9, the air chamber 16. The remaining elements of the model may be basedupon unsteady momentum balances on carefully chosen control volumescontaining the water in the jig body, the region around the bedplate 24and the solids and water in the region above the bed plate. Thesemomentum balances must consider energy losses from flow through the bedplate and the bed of particles. The mathematical model may be formulatedas a coupled set of first order differential equations and the solutionto the equations is generally computed from a set of initial conditionsand a description of the opening and closing times or general modulationof the apertures of the inlet and exhaust valves 11 and 10 and aknowledge of the flow through the air supply valve 6 and the flowthrough the hutch water supply valve 21. In some cases of jig design,additional elements such as the refuse elevators may have to beconsidered in the model as the pressure variations in the jig may causevariations in the water level in the refuse elevators (not shown inthese diagrams). The mathematical model has various constant parametersimbedded in it which relate to the physical dimensions of the jig andthe characteristics of flow through the bed plate and should be capableof providing a solution which accurately matches the measured watermotion in the jig, for a given set of operating conditions, with andwithout solids in the jig. The model also contains parameters relatingto the characteristics of the flow through the solids in the jig.

The control system may operate in the following steps.

Firstly, when solids are not being fed to the jig (no flow in stream26), the controller may cause the jig to pulse with the air controlvalve(s) operating in a particular sequence or so as to cause a certainmass flow of gas into the air chamber 16. The controller may furthercause the average water level in the air chamber (measured by sensor 13)to vary from time to time by changing the settings on the air controlvalves. From the information recorded from the sensors, the controllermay determine by non-linear parameter estimation techniques, estimatesof all model parameters in the mathematical model of the jig other thanthose which relate to the solids to be separated. This exercise ofon-line parameter estimation need not in principle be carried out veryfrequently as the sought-after parameter values will be influenced onlyby wear of parts or defects or parts in the jig (such as blinded bedplates, leaks, faulty valves and the like). In fact, comparison ofconsecutive patterns of measured signals or of consecutive sets ofestimated parameter values can be used to indicate specific faults inthe jig. Included within the scope of the control system is thedetermination of parameter values at some time interval, not necessarilyas a standard component of the control system, and the imbedding of thebasic parameters in the mathematical model.

Secondly, when solids are being fed to the jig, the measured values as afunction of time within the jig cycle can be used in conjunction withthe mathematical model to determine the characteristics of the particlebed in the jig with respect to flow through the bed. The estimation ofthe bed properties is carried out in a similar manner to that used toestimate jig parameters with no solids in the jig.

Consider that the water motion wave form in the jig chamber (derivedfrom pressure sensor 18 or the level sensor 13) departs from the desiredset point wave form (note here that the set point is not considered tobe a single numerical value rather the set point is a specified functionof time; one way to reduce such a specified function is to describe thefunction as a finite Fourier series of order N which requires 2N+1constants and a fundamental frequency) Using the mathematical model withthe imbedded constants characterising the solids bed and the othercharacteristics of the jig, it is possible to calculate the changes inthe settings to the inlet and exhaust air valves 11 and 10 and to thesupply valve 6 that when applied to the valves will return the watermotion to the set point wave form or nearly so. Such a control procedureapplied to the jig is not a simple feedback procedure, but it is anadaptive model-based control system and may be applied in consecutivesteps to achieve desired control actions.

Various means may be used to determine the valve settings that willreturn the water motion wave form to its set point wave form. Forexample, for a variety of particle bed characteristics (total mass andpressure drop constants) the values of the coefficients in the Fourierdecomposition of the resulting water wave form may be determined fromthe model as functions of the air valve settings (expressed either interms of Fourier decompositions of the wave form applied to each valveor in terms of opening and closing times). Then this functionalrelationship may be used to determine the valve settings required forthe desired wave form by inverting the functional relationship.Alternatively, the model may be used in conjunction with amulti-dimensional minimisation procedure to seek the valve settings thatprovide the desired water wave form. These calculations are carried Outin the controller while executing such other control functions as may beimplemented. In such a case, the controller will be a numericalprocessor capable of carrying out all calculations in parallel under theoverall control of a master processor.

This water wave form control procedure may be carried out in conjunctionwith other control procedures. For example, the bed gauging device 20,which may be a nucleonic or some other form of device that indicates theextent of bed dilation or variation of bed bulk density as a function oftime within the jig cycle, may be used to regulate the rate of dischargeof high density material from the jig via device 23. In general, thesimultaneous operation of such control loops is important as thestability of jig operation is sensitive to interactions betweenpulsation (water wave form) and discharge of high density material. Forexample, in a situation where the amount of high density material in thefeed stream 26 increases, there must be a corresponding increase in themass flow of high density material past the device 23 into the bottom ofthe jig. If there is not such an increase in mass flow past device 23,the mass of solids in the jig bed will increase and this will generallycause the amplitude of the water wave form to decrease. Such decrease inamplitude will in turn slow the rate of transport of solids along thejig from the feed point to discharge point and lead to further increasein mass of solids in the bed. This situation is clearly unstable but canbe ameliorated by maintaining the water wave form in the jig. Thecombination of water wave form control and control of the rate ofdischarge of high density material from the jig based on the signal froma bed sensor 20 as described provides a better control of the separationcharacteristics of the jig than can be achieved by either type ofcontrol loop alone.

It is to be noted that, in general, all the sensors indicated arerequired to implement a control system as described above. Inparticular, the temperature sensors 8 and 12 are used to provideinformation necessary to the modelling of the behaviour of the gas phasein the air chest and the air chamber. Industrial jigs that are suppliedwith air by throttling the air through a valve operate with the gas inthe air chest and chambers substantially above ambient temperature andthe operating temperature of the gas may vary with the operatingconditions of the jig. The pressure sensors 7, 22 and 18 are alsorequired, in general, to determine the parameters of the mathematicalmodel describing the behaviour of the jig. Device 20 may also beequipped with a plurality of pressure sensors arrayed at differentheights within the jig bed.

One may also consider the case of a piston or diaphragm jig. The Kelseycentrifugal jig is also a variant of the piston jig. In all these jigs,there is no air chamber and the pulsation is produced directly using amechanically or electromagnetically driven solid body in direct contactwith the liquid in the jig. Oscillation of the solid body produces waterpulsion through the bed plate. In the case of such directly driven jigs,the mathematical model of the jig that provides a description of thewater or fluid motion in the jig becomes, in some respects, quitetrivial in so far as the direct coupling from the driven mechanism tothe liquid in the jig body guarantees water motion of a particular waveform unless the body of the jig deforms under the influence of pressure.In such a case, many of the sensors shown in the FIGS. 1 and 2 areunnecessary and the pressure sensor 18 and the bed gauge 20 are veryimportant. Note also, in the Kelsey jig, that there is no dischargedevice 23 and that high density product is collected in the hutch bypassing through the bed plate 24. Also, the bed consists of a relativelythick layer of ragging (generally a solid material of densityintermediate between that of the high density product and that of thelow density product and coarser than the material to be separated) and athinner bed of feed material on top of the ragging.

In the example of the Kelsey jig, the control objectives are two-fold.Firstly, the normal operation of the jig must be monitored and secondly,the operation of the jig must be controlled to maintain adequatethroughput and separation. A mathematical model that relates thepressure under the bed plate to the characteristics of the bed can beconstructed in the same way as for a conventional jig. Since thedisplacement waveform of the driving body is guaranteed unless the drivebreaks down, the pressure beneath the bed plate can be determined as afunction of the displacement of the driving body and the bedcharacteristics. This pressure can then be expected to show a particularvariation of pressure beneath the bed as illustrated in FIG. 3.

The separation in the jig depends in part upon there being adequatedilation of the bed, so that the high density particles can pass fromthe feed side of the bed towards the bed plate at a reasonable rate.This dilation in turn depends upon the pulse of water through the bedplate being adequate to lift the bed. The point of lifting of the bed ischaracterised by the point in the pressure wave form where the pressureis above the average value and becomes approximately constant. If thepressure wave form does not display the correct shape and magnitude, itcan then be deduced that the conditions in the bed have changed. Indeed,in the same way as can be done in a conventional jig, the bedcharacteristics (flow parameters) can be estimated using themathematical model of the jig. A typical disturbance to the conditionsin the bed is a change in the total mass flow of solids to the separatoror a change in the content of high density material in the feed, orboth. All these conditions result in a change in the required mass flowof high density material through the bed plate. The control action thatis required in response to particular changes in the pressure wave formvaries according to the nature of the change and the nature of theseparation being carried out. One may consider making a change in hutchwater flow, or a change in throughput of feed solids, or a change infrequency of pulsation or ultimately, a change in amplitude of pulsionwith the final object of restoring the indication in the pressure waveform of dilation to a desired state.

With reference to the pressure wave form in FIG. 3, the time period ofthe `clipped` portion of the wave form (i.e. from approximately 55% to95% of the cycle period) must be at least equal to, and preferablygreater than, the time for the voidage wave to travel up through the bedensuring that the bed is fluidised on each cycle. If the time period isless than the voidage wave travel time, the bed is not fully dilated andeffectively acts as a screen or sieve, with respect to the particles tobe separated. Any partial screening of the bed, when only partialdilation occurs, will restrict the movement of larger diameter higherdensity particles towards the bottom of the bed.

The present invention is the first recognition that the wave form of thewater pressure in the jig can provide a set point for the control of thejig.

Various changes and modifications may be made to the embodimentsdescribed and illustrated without departing from the scope of thepresent invention defined in the appended claims.

We claim:
 1. A method of monitoring jig separators for minerals in a bedon the jig, comprising the step of:measurement of a time variation witha jig cycle of at least one signal responsive to an operating parameterselected from the group consisting of bed voidage, water level, velocityor acceleration in a jigging or air chamber, particle velocity oracceleration in the bed and water or air pressure.
 2. A method ofautomatic control of jig separators for minerals in a bed on the jigincluding the steps of:using a form of the time variation within a jigcycle of at least one signal, responsive to an operating parameterselected from the group consisting of bed voidage, water level, velocityor acceleration in a jigging or air chamber, particle velocity oracceleration in the bed and water or air pressure, wherein:one or moreof the operating parameters of the jig are manipulated in order toproduce a sought-after form of time variation of the signal within a jigcycle.
 3. A method as claimed in claim 2, wherein:the operatingparameters are selected from one or more of the members of a groupconsisting of:(i) control of inlet or outlet air valve port area in airdriven jigs; (ii) control of opening and closing times of air valves inair driven jigs; (iii) control of operating air supply pressure in airdriven jigs; (iv) control of the mass flow of gas into an air chamber bya combination of (i) and (ii); (v) control of oscillation frequency ofany kind of jig; (vi) control of a diaphragm motion in diaphragm orcentrifugal jigs; (vii) control of motion of a bed plate in moving platejigs; (viii) control of centrifugal force in centrifugal jigs; and (ix)control of a mean level of water in an air chamber of an air driven jig.4. A method as claimed in claim 3 wherein:a manner of determination ofcontrol actions to be applied to the operating parameters is bycontrollers functioning in an analog or digital fashion and includescomputational analyses of signals and jig responses via Fourierdecomposition methods.
 5. A method as claimed in claim 4 wherein:themanner of determining the control action includes a real-timecomputation of expected jig response to a control action using amathematical model of the jig; and the control action to be takenadditionally includes the real-time estimation of physical parameters ofthe jigging system, including bed mass or bed pressure drop, followed bycalculation of jig operating settings, both using a mathematical modelof the jig.
 6. A method as claimed in claim 5 wherein:the method ofcontrol is a feed-forward control of the jig combined with real-timeidentification of jig parameters, or a self-tuning control of the jig.7. An apparatus for monitoring or control of jig separators for mineralsin a bed on the jig, comprising:means for measuring a time variationwithin a jig cycle of at least one signal responsive to an operatingparameter selected from the group consisting of bed voidage, waterlevel, velocity or acceleration in a jigging or air chamber, particlevelocity or acceleration in the bed and water or air pressure.